A vehicle door frame in which an upright pillar sash, which extends in the vertical direction of the door, and an upper sash, which forms the upper edge of the door, are joined together at a door corner portion is known in the art (Patent Literature 1). As a joining structure at the door corner portion, a type of joining structure in which an upper part of the upright pillar sash is obliquely cut off to form a joining surface and in which the upper sash is joined to this joining surface is known in the art.